1. Field of the Invention
The present invention generally relates to the construction of building exteriors and more particularly to a system and method for constructing a cladded exterior wall of a building such as a stucco exterior wall to seal the wall and prevent damage from the ingress of water and insects into the structure of the exterior wall.
2. Background of the Invention and Description of the Prior Art
The exterior walls of residential and commercial buildings are clad with a variety of materials and construction. Apart from structural considerations, the cladded exterior walls of such buildings must withstand all sorts of weather, in a wide-ranging gamut of temperatures, water and other forms of precipitation, wind, solar radiation, and other meteorological conditions. Other considerations include resistance to damage by insects and other animals or by plants and trees. In addition, to conserve energy it is crucial that such walls be well insulated against the transmission of heat through the walls.
In a typical building, for example, a wood-framed residential house, the wood framework is covered with a wall sheathing secured to the wood framework. Such exterior wall sheathing may be wood panels or composite wood-based or felt or pressed-fiber panels, sometimes covered with a heavy paper or moisture barrier. The outside surface of the exterior walls may then be covered or clad with siding materials of wood, metal, or synthetic materials; brick or stone work; or a stucco wall system.
In a conventional process, stucco is a composition of aggregates, water, and a binder that is prepared and applied as a thick liquid or slurry to a surface, usually in several coats, and allowed to harden into a dense, hard surface that is generally durable and weather-resistant. The aggregate material is typically lime, although sand, synthetic aggregates, glass fibers, or Portland cement are commonly used. The wall surface to which the stucco mixture is applied is generally prepared by installing lath—a type of lattice or wire mesh to support the wet mixture as it hardens.
While stucco is a versatile material, that also lends itself to many decorative treatments, it is brittle and its long term durability depends substantially on the skill of the craftsman employed to apply it. It is susceptible to cracking as a building structure, settles, flexes with movement of the earth, similarly to gypsum wall board, etc. Thus, unless openings in the stucco coating are properly finished, particularly along the top and bottom edges, around pass-through fixtures for plumbing or electrical lines, windows and doors, etc., the integrity of a stucco exterior may be seriously weakened, Moreover, one commonly used construction technique requires formation of a drainage plane between the exterior wall and the insulating panel (or the stucco layers if no insulating panel is used). An example of this system is the so-called Exterior Insulation and Finish System or “EIFS.”
The EIFS structure requires a drainage plane formed by vertical passages on the back side of insulating panels that are included between the exterior wall and the stucco layers. The drainage plane provides passages in a thin space between the exterior wall sheathing and an insulating panel, either with grooves formed in the back side of the insulating panel or by troweling vertical paths in the adhesive layer that is used to secure the insulating panel to the exterior wall surface. The passages thus provided theoretically allow drainage of water that may find its way inside the wall so that it does not accumulate and cause damage to the wall (e.g., rot) or accumulation of fungal substances (e.g., “mold”), However, unless the EIFS structure is properly installed, the symptoms of water condensation or accumulation in the thin drainage plane spaces, or insect (e.g., termite) damage, or even mold contamination may go unnoticed—often for years—until the damage is so severe that the wall must be entirely removed and replaced to repair the damage. Accordingly, the formation of the drainage plane, and the long-term durability of the EIFS structure depends critically on the proper formation of the thin space between the exterior wall and the insulating panel of stucco. For example, if the space is too thin, water may become trapped in the space due to surface forces. Or, if the drainage spaces formed by troweling are not all vertically-oriented, water may become trapped within the non-vertical portions of the drainage spaces.
Thus, in balance, stucco exterior walls, whether constructed according to conventional methods or the EIFS method, are susceptible to substantial damage due to water originating generally from weather events. Such events provide numerous and varied opportunities for water to enter and become trapped in the interstices of an exterior wall, especially stucco exterior walls. Experience with repairing damage to stucco-clad exterior walls demonstrates that it is not enough to (1) install a stucco exterior wall surface by conventional methods without limiting opportunities for water to find its way into the stucco structure through openings, cracks or other defects. It is not enough to (2) use a finish coat of flexible acrylic—as is sometimes recommended—to cover the exterior so that when cracks develop they are “bridged” by the flexible coating. It is not sufficient to (3) include drainage planes that provide thin spaces for moisture to condense or collect and that are sensitive to the process technique(s) required to install them properly. It is not enough to (4) provide a weep screed at the lower edge of the stucco wall if that portion of the wall is susceptible of pooling water or the screed is improperly installed.
There is thus a need for a system and method for constructing exterior wall cladding, including stucco finishes, which provides a wall that is thoroughly waterproof; does not allow the ingress of water or moisture, and is able to withstand all kinds of contacts with water in any form without loss of integrity or durability.